Patent GB-1154992-A (GB)
Title: Control Systems
IPC: F16D23/02
Filed: 1967-10-25
Abstract: 1,154,992. Turbines; gas turbine plant. FORD MOTOR CO. Ltd. Oct. 25, 1967 [Nov.14, 1966], No.48439/67. Headings F1G and F1T. [Also in Division F2] To facilitate ratio shift in a motor vehicle change speed gear which is driven from the power turbine of a gas turbine engine 158 through a main clutch 160, the engine shaft 166 is braked during clutch disengagement to prevent its speed increasing or to synchronize the driving and driven clutch plates 162, 164. The engine shaft 166 is braked by rotating the engine flow directing blades as nozzles (1, Fig.2, not shown) from a driving position (4) to a braking position (6). The nozzles (1) are rotated by a servomotor 10 under the control of a valve 14. The spool 68 of the valve 14 is biased towards a central position by springs 74, 76 which react on cam followers 78, 80 engaging cams 92, 100. The cam 92 is fast with a rotatable valve spool 94 which carries a lever 98 connected to the vehicle accelerator pedal. On depression of the accelerator pedal the cam 92 rotates and permits the follower 78 to move left whereupon the spring 76 moves the valve spool 68 left to connect a pressure liquid supply duct 72 through line 48 to the right side of the servopiston 34. As the piston 34 moves left to rotate the nozzles (1) to a driving position a follow-up linkage 106 rotates the cam 100 which permits the follower 80 to move right until the value spool 68 is returned to the central position. The position of the piston 34 thus corresponds to accelerator pedal position. When the valve spool 94 is in the engine idle position radial ducts 120, 121 therein are aligned with orifices 122, 123 and pressure liquid from the duct 72 is supplied through a vehicle speed responsive valve 126, the orifices 122, 123 and a central duct 119 in the valve spool 94 to a chamber 86 having a permanent bleed orifice 88. As pressure builds up in the chamber 86 the follower 78 and valve spool 68 are moved right to connect the supply duct 72 through duct 46 to the left side of piston 34 which is thus moved left to pivot the nozzles to their braking position. If the vehicle speed is below a predetermined value a spring 136 moves the spool 128 of the valve 126 down to the position shown in which pressure liquid is supplied to the chamber 86 through the orifice 123 alone. If the vehicle speed is above the predetermined speed the spool 128 is moved up by speed responsive pressure liquid acting through a port 140 so that pressure liquid is supplied through both orifices 122, 123 to chamber 86 for increased braking. A value 20 normally connects the orifice 123 to the speed responsive valve 126 but is rotated when the clutch pedal 165 is depressed to connect the orifice 123 to a line 156 supplied with pressure liquid through a regulating valve 200 at a pressure proportional to engine shaft-speed. The spool 220 of the regulator valve 200 meters liquid from an inlet 210 to an outlet 212 connected to the line 156 in accordance with the pressure differential in end chambers 224, 226. When the pressures in chambers 224, 226 are equal springs 234, 236 move the valve spool to a position closing the outlet 212. An accumulator 228 minimizes sudden pressure fluctuations in chamber 226. A governor valve 168 rotatable with the engine shaft 166 produces a pressure proportional to engine shaft speed which pressure is applied directly and through a restrictor 240 to the chambers 224, 226 respectively. During clutch disengagement an increase in engine shaft speed causes an increase in pressure in the chamber 224 which moves the valve spool 220 left to increase the pressure supplied through line 156 and orifice 123 to chambers 86. The pressure increase in chamber 86 produces increased braking of the shaft 166 which is thus slowed to its former speed. During such a temporary rise in engine shaft speed the pressure in chamber 226 remains substantially constant due to the restrictor 240 and accumulator 228. In Fig. 7 (not shown) the chamber (226<SP>1</SP>) of the valve 200 is fed directly by a governor valve rotatable with the clutch driven plate 164 and thus the pressure in line 156 is regulated to brake the engine shaft 166 until the clutch plates 162, 164 are synchronized.